Abstract Triploid Atlantic salmon (Salmo salar) aquaculture has been extensively considered for many years, but its development has so far remained very limited. This is mostly due to poorer farming performances of triploid fish (3 N) in comparison with their diploid (2 N) counterparts, with temperature seen as a key explanatory factor. Furthermore, there are many inconsistencies between studies and considerable knowledge gaps exist in triploid physiology and performance, especially at early life stages. The present work is a pilot experiment in which the temperature was kept constantly low (8 °C) during 149 days from 81 to 229 days post hatching (dph). We used a multi-trait approach with an emphasis on behaviour to investigate the performance of 3 N and 2 N Atlantic salmon. Specifically, we compared growth, survival, prevalence of malformation, gut microbiome, and behavioural traits such as swimming activity in response to a stressor, and boldness. Reared at a cold and constant temperature, juvenile triploid and diploid fish showed similar growth from 81 to 165 dph but a difference occurred at 221 dph. Interestingly, triploids outperformed diploids in terms of survival. The prevalence of deformity was low in both diploid and triploid fish and no lower jaw skeletal abnormalities were observed in live fish at the end of the experiment. Triploid and diploid fish displayed very similar swimming activity and boldness traits as well as a very similar gut microbiome. This multi-trait approach reveals that when raised at low temperature, triploid and diploid fish performed equally well, with even a better survival for triploids towards the end of the experiment. Our study emphasizes the need for developing different rearing protocols for diploid and triploid Atlantic salmon. Applying a lower temperature at early developmental stages in ectotherms inevitably slows their developmental rate and may allow fine tuning of key developmental structures, decreasing deformities at early and later life stages of triploids. Further research comparing different temperature profiles is needed to find the best compromise between growth performance and low malformation rate and to examine the long-term effect of low temperatures applied at an early stage of development. This is a crucial step to improve both triploid salmon performance and welfare.

中文翻译：

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三倍体对低温饲养大西洋鲑（Salmo salar）幼鱼性能、肠道微生物组和行为的影响

摘要 三倍体大西洋鲑（Salmo salar）水产养殖已被广泛考虑多年，但迄今为止其发展仍然非常有限。这主要是由于三倍体鱼 (3 N) 与其二倍体 (2 N) 对应物相比的养殖性能较差，温度被视为一个关键的解释因素。此外，研究之间存在许多不一致之处，并且在三倍体生理和性能方面存在相当大的知识差距，尤其是在生命早期阶段。目前的工作是一项试点实验，在孵化后 (dph) 的 81 至 229 天的 149 天内，温度始终保持在较低水平 (8 °C)。我们使用了一种强调行为的多特征方法来研究 3 N 和 2 N 大西洋鲑鱼的性能。具体来说，我们比较了生长、存活、畸形的发生率、肠道微生物组和行为特征，例如应对压力源的游泳活动和胆量。在低温和恒温条件下饲养，三倍体和二倍体幼鱼在 81 至 165 dph 时表现出相似的生长，但在 221 dph 时出现差异。有趣的是，三倍体在存活率方面优于二倍体。二倍体和三倍体鱼的畸形发生率都很低，实验结束时在活鱼中没有观察到下颌骨骼异常。三倍体和二倍体鱼表现出非常相似的游泳活动和胆量特征以及非常相似的肠道微生物组。这种多性状方法表明，在低温下饲养时，三倍体和二倍体鱼的表现同样出色，在实验结束时三倍体的存活率甚至更高。我们的研究强调需要为二倍体和三倍体大西洋鲑鱼制定不同的饲养方案。在变温动物的早期发育阶段应用较低的温度不可避免地会减慢它们的发育速度，并可能允许微调关键发育结构，减少三倍体生命早期和晚期的畸形。需要进一步研究比较不同的温度曲线，以找到生长性能和低畸形率之间的最佳折衷，并检查在发育早期应用低温的长期影响。这是提高三倍体鲑鱼性能和福利的关键步骤。在变温动物的早期发育阶段应用较低的温度不可避免地会减慢它们的发育速度，并可能允许微调关键发育结构，减少三倍体生命早期和晚期的畸形。需要进一步研究比较不同的温度曲线，以找到生长性能和低畸形率之间的最佳折衷，并检查在发育早期应用低温的长期影响。这是提高三倍体鲑鱼性能和福利的关键步骤。在变温动物的早期发育阶段应用较低的温度不可避免地会减慢它们的发育速度，并可能允许微调关键发育结构，减少三倍体生命早期和晚期的畸形。需要进一步研究比较不同的温度曲线，以找到生长性能和低畸形率之间的最佳折衷，并检查在发育早期应用低温的长期影响。这是提高三倍体鲑鱼性能和福利的关键步骤。需要进一步研究比较不同的温度曲线，以找到生长性能和低畸形率之间的最佳折衷，并检查在发育早期应用低温的长期影响。这是提高三倍体鲑鱼性能和福利的关键步骤。需要进一步研究比较不同的温度曲线，以找到生长性能和低畸形率之间的最佳折衷，并检查在发育早期应用低温的长期影响。这是提高三倍体鲑鱼性能和福利的关键步骤。